Belt sander



Sept. 9, 1969 R, Q FQQDY ET AL BELT SANDER 2 Sheets-Sheet l Filed July 27, 196e /NvE/vrons 00d? 30325K @,MZN ATTORNEYS Sept. 9, 1969 R o, FOQDY ET AL 3,465,479

BELT SANDER Filed July 27. 1966 2 Sheets-Sheet 2 United States Patent O 3,465,479y BELT SANDER Raymond O. Foody, Chicago, and Harold Raymond Botefuhr, Bensenville, Ill., assignors to G. W. Murphy Industries, Inc., a corporation of Texas Filed July 27, 1966, Ser. No. 568,223

Int. Cl. B24b 21/18 U.S. Cl. 51-148 12 Claims ABSTRACT OF THE DISCLSURE Surface dressing belt sander with an idler roller having an offset, rotatably mounted belt guide means and resilient means for tensioning the belt. The idler roll is supported by a yoke member which is adapted to be releasably latched in a collapsed position such that a surface dressing belt can be readily inserted over the sander rolls.

This invention relates to portable surface dressing devices and more particularly to an improved surface dressing tool of the continuous belt type.

A principal object of this invention is to provide a surface dressing tool having improved means for guiding a surface dressing belt along a predetermined path.

Another object of this invention is to provide a surface dressing tool having improved means for mounting the rolls for tensioning the surface dressing belt.

Still another object of this invention is to provide a surface dressing tool having improved means for latching one of the rolls in a collapsed position to facilitate adding or removing a surface dressing belt from the rolls.

And another object of this invention is to provide a surface dressing tool having improved means for guiding a surface dressing belt which means is driven by said belt.

A further object of this invention is to provide a surface dressing tool having improved quick release means for the roll latching means whereupon a surface dressing belt can be snugly and resiliently tensioned on the rolls instantaneously.

And a further object of this invention is to provide a surface dressing tool having improved means for mounting the idler roll so that it will track relative to the driving roll so as to retain a surface dressing belt thereon.

Yet another object of this invention is to provide a surface dressing tool having improved guide means that operate in such a way as to substantially eliminate wear of said guide means as the surface dressing belt traverses in contact therewith.

Further objects and advantages will become readily apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIGURE 1 is a perspective view of a belt sanding mechanism incorporating our invention;

FIGURE 2 is a cross sectional view taken along the lines 2-2 of the fragmentary view of FIGURE 5 with additional parts shown also in cross section;

FIGURE 3 is a cross sectional view taken along the lines 3 3 of FIGURE 2;

FIGURE 4 is an end View of the guide means and idler roll of FIGURE 2;

FIGURE 5 is an elevational View of the front half of the surface dressing tool of FIGURE 2-with parts broken away and parts in section;

FIGURE 6 is a partial cross sectional view of a modified form of the invention taken along the line 6-6 of FIGURE 7; and

FIGURE 7 is an elevational view of the front half of the modified form of surface dressing tool of FIGURE 6 with parts broken away and parts in section.

3,465,479 Patented Sept. 9, 1969 ICC While the invention is susceptible of various modifications and alternative constructions, it is herein shown and will hereinafter be described in a preferred embodiment and, more particularly, and embodiment especially adapted for use with a belted type sander. It is not intended, however, that the invention is to be limited thereby to the particular embodiment shown. On the contrary it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.

As shown in the drawings and for purposes of disclosure, the invention is illustrated as part of a portable electric belt sander having means for tensioning the sanding belt on the machine and having means for tracking and centering the sanding belt relative to the driver and idler rolls of the machine.

Latching means are provided for holding the idler roll in collapsed position relative to the driver roll so that a sanding belt can be removed and replaced on the machine. Means are provided for releasing the latching means whereupon the sanding belt will be tensioned by the action between the ixed driver roll and the resiliently loaded idler roll. The tracking and centering means is mounted in such a way that friction between the sanding belt and the housing is substantially eliminated as is friction between the sanding belt and the centering means, thereby elongating the life of the sanding belt and the machine housing.

As shown herein for purposes of disclosure, the surface dressing machine or device 10 has a housing or frame 11 comprising a mounting base 12 which supports the upstanding motor casing 14 containing a motor (not shown) and appropriate drive train (not shown) connected to the driver roll 16 through the gear 17 mounted on shaft 18. The mounting base 12 is substantially flat and is generally intended to be held substantially parallel to the surface being dressed. The base 12 has a vertically disposed side wall 19 downwardly depending therefrom along one side edge thereof. A downwardly directed rear wall 20 depends from said base 12 and joins said side wall 19 along one edge thereof. As shown in FIGURE 2, a pair of substantially parallel spaced apart support walls 22, 23 are connected to the side wall 19 approximately midway between the front and rear ends of said machine. The mid-portion of the lower edge of said side wall 19 and said support walls 22, 23 have attached thereto a supporting shoe 25 which lies substantially parallel to, spaced from and underneath said mounting base 12. As can be seen in FIGURES 3 and 5, the supporting shoe 25 is formed integrally with the wall 19 and support walls 22, 23 with the front and rear end portions 26 of the shoe 25 being curved upwardly therefrom.

The mounting shaft 18 is journalled for rotation about its axis by means of bearings 27, 28 mounted in the opening 29 in the inwardly and outwardly directed reinforced bearing hubs 30, 31 carried by the side wall 19. The driver roll 16 is keyed to said shaft 18 and has a cylindrical working surface 33 surrounded by a resilient sleeve 34. The sleeve 34 can be rubber or other material that has some resiliency and also has some frictional characteristics. The motor in the casing 14 drives the power train which in turn drives the gear 17, shaft 18 and driver roll 16.

An idler roll 40 is resiliently mounted in the housing in the end portion removed from the driver roll 16. The idler roll 40 is composed of two halves 41, 42 which are mounted in juxtaposed relation for rotation about a common nonrotating shaft 43 by means of sleeve type bearings 45, 46 surrounding the shaft and engaging in the hollow openings in the two halves 41, 42, respectively. An end cap retainer 47 is secured to the end of the shaft 43 by means of the screw -48 for preventing the roller 3 half 41 from coming off the shaft 43. A retainer 50, which will be described more in detail hereinafter, is secured by screw 51 to the other end of the shaft 43 for holding the roller half 42 on said shaft 43.

A mounting yoke 52 serves to position the idler roll 40 on the mechanism and is comprised of a Y-shaped body member 53 having a pair of oppositely disposed hubs 54 formed on the base leg 55 of the Y. The hubs 54 are secured rigidly to the shaft 43 and are nested in undercut portions of the roller halves 41, 42 so that the roller halves 41, 42 can rotate relative to the shaft 43 and hubs 54 without interference therebetween.

The spread arms 57, 58 of the member 53 have radially enlarged portions 60 into which are secured the spaced apart rods 61, 62 extending away from the base leg 55 of the Y and having their axes lying in a plane common to each other and common to the axis of the shaft 43. The rods 61, 62 each have two spaced apart reduced diameter portions 63, 64 and 65, 66 respectively. The axial lengths of the portions 63, 65 are equal to each other and are shorter than the axial lengths of the portions 64, 66. The rods 61, 62 slidably pass through aligned openings 68, 69 and 71, 72 respectively, formed in the spaced apart walls 22, 23. A retaining washer 74 such as a snap ring is seated in the portion 63 of the rod 61 on the remote side of the wall 22 so as to retain the idler roll 40 secured to the base 12.

A pair of relatively strong compression springs 76, 77 are positioned around the rods '61, 62 and bear against the support wall 23 and the enlarged portion 60 of the member 53 for urging the idler roll 40 away from the driver roll 16. The retainer washer 74 prevents the idler roll 40 from moving too far away from the driver roll 16.

A latching means is provided for holding the idler roll 40 in the collapsed position and comprises, as shown in FIGURES 2, 3 and 5, a generally U-shaped slide bar 80 having a base portion 81 and side legs 82, 83. A pair of elongated openings 85, 86 are formed through the portion 81 in predetermined spaced apart relationship with the rods 61 and 62 passing respectively therethrough. The leg 83 lies parallel to the wall 19 such that a compression spring 88 nested in a recess 89 in said wall 19 bears against said leg 83 to urge the latching bar 80 away from the wall 19 with the wall of the opening 86 l bearing against the side of the rod 62.

Applying pressure on the idler roll 40 in the direction of the driver roll 16 will slide the rods 61, 62 through the openings 68, 69 and 71, 72 respectively, in the walls 22, 23 until the reduced diameter portion 66 becomes aligned with the edge of the opening 86 whereupon the spring 88 drives the latch bar 80 away from the wall 19 with the one edge of the opening 86 nested in the portion 66 for holding the idler roll 40 in the collapsed position. Release of the pressure on the idler roll 40 will not return the roll to its initial position, but inward pressure on the portion 82 of the latch bar 80 will unseat the bar from its holding position with respect to recessed portion 66, whereupon the springs 76, 77 will drive the idler roll forward until the ring 63 engages wall 22 or until the idler roll 40 and driver roll 1'6 engage the inside of a continuous belt surface dressing member 90. The member 90 can be removed by rearward movement of idler roll 40 as hereinabove described.

The axis of the shaft 43 is canted slightly with respect to the axis of the shaft 18 such that, as seen in FIGURE 2, the axis of the idler roll 40 tilts or toes slightly inward toward the axis of the `driver roll 16 on the side of the surface dressing machine away from the wall 19. In this way the belt 90 will have a tendency to climb or work up the inclined plane toward the wall 19 and into co'ntact with a guide means to be described hereinafter.

The surface dressing member 90, when wrapped around the idler roll 40 and driver roll 16, has a return stretch 92 thereof closely spaced beneath the base 12 and has a working stretch 93 exposed below the machine for dressing a surface. The backing member 25 bears against the inside of the member throughout most of the working stretch 93 for backing the dressing member 90 during use.

For holding the surface dressing member 90 centered on the rolls 40 and 16, an improved guide means is provided on the one side of the idler roll 40. That is, the retainer 50 is nested in a recess in the one end of the shaft 43 and has a stepped configuration with the smallest diametered portion 97 nesting in said recess in the shaft 43. The intermediate or next larger circular portion 98 of the retainer 50 has a center displaced radially with respect to the center of the portion 97 and the largest circular portion 99 has a center coinciding with the center of the portion 98. All three portions 97, 98, 99 are formed integrally with each other to produce the retainer 50 with the screw 51 passing therethrough along the centerline of the intermediate and large portions 98, 99 and into an opening 101 in the shaft 43 along an axis offset radially with respect to the centerline of said shaft. Since the shaft 43 does not rotate, the retainer 50 will likewise not rotate relative thereto.

A guide means 103 for the surface dressing means 90 is rotatably mounted on the retainer 50 and comprises a guide disc 104 which is circular in shape and slightly larger in diameter than the idler roll 40. The disc 104 has an enlarged stepped aperture 105 through the center portion thereof. The aperture 105 has the reduced diameter stepped portion 106 which is adapted to intert with the intermediate portion `98 of the retainer 50 such that the disc 104 is retained in a rotatably mounted relationship on the retainer 50 and idler roll 40. Since the axis of the portions 98, 99 of the retainer 50 is offset upwardly with respect to the axis of the shaft 43, the disc 104 will rotate about said axis with edge portions overlapping upwardly with respect to the idler roll 40.

The disc 104 being larger in diameter than the idler lroll 40 and having its axis displaced upwardly relative to the axis of the shaft 43, will produce an overlapping of the edges of the disc with respect to the idler roll. The disc 104 is mounted so that the bottom edge of the disc will not overlap the idler roll 40 at the bottom, but will overlap in a gradually increasing fashion forwardly and upwardly from the idler roll. The disc is free to rotate freely about its axis relative to the idler roll 40.

In operation, with a surface dressing belt 90 in position about the rolls 16 and 40, and due to the slight canting of the idler roll 40 toward the driver roll 16, the inner edge of the belt will engage with the disc 104 and will move the guide means or disc with it as it rotates about the idler roll 40. Since the disc 104 overlaps the upper edge of the roll 40 and rotates about its axis offset with respect to the axis of the roll 40, the belt will engage with and rotate said disc 104 while the disc is holding said belt centered on said rolls 40 and 16. The movement of the disc 104 by the belt 90 substantially eliminates friction therebetween, lengthening the life of the belt. Also, the disc eliminates the friction plate previously required in the housing against which the belt rubbed during use, thereby not only reducing the cost of the housing, but also eliminating the need for frequent replacement of the friction plate.

FIGURES 6 and 7 show modified forms of the im- -proved idler roll latching means 110 and belt guide means 112, with the remaining parts of the surface dressing mechanism being the same as described in FIGURES 1-5. The latching means 110 is comprised of an idler roll 114 mounted on the forward end of the Y-shaped yoke with a pair of rearwardly facing openings 116 in the ends of the arms 113 of the Y. Each opening 116 has one end portion of a hollow sleeve member 117 slidably disposed therein with the other end portion of said sleeves 117 seating in blind apertures 118 formed in a solid support portion 120 of the support walls 121, 122. The Walls 121, 122 are formed integrally with the wall 19 carried by the base 12 and support a backing plate 123 in position substantially parallel to said base 12. The backing plate 123, in addition to being shown as formed integrally with the walls 121, 122, is also formed integrally with the lower edge portion of the wall 19 and has a :front edge portion 125 curved upwardly out of the plane of the backing surface of the plate to serve as a guide for the surface dressing belt 90 as `well as to provide an area wherein a wear plate 126 can be removably fastened over the backing surface by means of screws 127.

A solid plug 129 is slidably telescoped into the end of each sleeve 117 and has one end bearing against the base of the openings 116 in the Y-yoke 115 and has its other end bearing against a compression spring 130 contained in the sleeve 117 between said plug 129 and the bottom of the aperture 118 in the support 120. The relative fit between the sleeve 117 and the walls of the openings 116 in the yoke 115 is such that a dashpot effect can be created therebetween. That is, due to the fit, there is no rapid movement between the yoke and the support 120, as will be described hereinafter.

A latch arm 132 is pivoted by pin 133 to a lug 134 formed on the top surface of the support portion 120 and has a spring 136 bearing between the portion 120 and the arm 132 so as to urge the latching prong 138 downwardly toward the Y-yoke 115. A release plate 140 is formed on the end of the arm 132 opposite to the prong 138 and extends laterally sidewise so as to be readily acessible to depress when it is desired to release the idler roll 114 from the collapsed position. A stop lug 141 is formed on the top surface of the Y-yoke 115 midway between the arms 113 and in position to` be engaged by the sprong 13S on the latch arm 132. The rear surface of the lug 141 is sloped to guide the prong 138 upward as the idler roll 114 is depressed rearwardly against the force of the springs 130 so that upon reaching the top of the slope, the spring 136 will pivot the arm 132 so that the prong 138 will drop in front of the lug to hold the idler roll 114 in the depressed or collapsed position. Downward pressure on the release plate 140 will pivot the arm 132 to disengage the prong 138 from the lug 141 whereupon the springs 130 will drive the idler roll 114 forward. Due to the dashpot fit between the sleeves 117 and the openings 116 the roll 114 will be moved forward at a relatively slow pace as the vacuum inside the sleeves 117 and the openings 116 gradually fill with air seeping past said sleeves and the walls of the Openings. The relatively slow movement of the idler roll 114 into nestedr relation with the belt 90 will prevent damage to the belt and at the same time not detract from the holding ability of the rolls with the belt since when the roll is fully in position the dashpot will not have any restraining effect on the springs 130;

The idler roll 114 has its axis canted toward the axis of the roll 16 and has the shaft 43, separate roll halves 41, 42, bearing sleeves 45, 46, retaining washer 47 and screw 48, all substantially as described with respect to FIG- URES 1-5. The roll half 42 has an end portion which is recessed at 143 and into which is nested a bearing ring 144 having radially directed slots 145. The ring 144 is fixed relative to the roll half 42.

A retainer 150 is nested in the recess 151 in the end of the shaft 43 and is held to said shaft by means of a screw 153 passing through said retainer 150 and into said shaft along an axis offset radially with respect to the center axis of said shaft 43. In this way, the retainer and shaft are assured of no movement relative to each other. The retainer 150 has an outwardly extending bearing surface 155 which is circular in shape with the center of said circle displaced upwardly and rearwardly from the center of either said shaft 43 or said screw 153 so as to create an eccentric surface relative to the axis of the shaft. A guide disc 156 is lmounted for rotation about said bearing surface 155 of the retainer and comprises a circular disc shaped body portion which has an outside diameter slightly larger than the diameter o-f the idler rolls 41, 52. A

large opening 157 is formed through the center of the disc into which is slidably nested the bearing surface 155 of the retainer. A pair of lugs 159 are formed on the one surface of the disc 156 and project axially inwardly therefrom into coacting relationship with the walls of the slots formed in the bearing ring 144. A washer 160 is secured between the head of the screw 153 and the retainer with the edges of said washer 160 overlapping the recessed portion of the disc 156 so as to secure the guide plate or disc 156 to the idler roll 42.

In use, the shaft 43, retainer 150, washer 160 and screw 153 are all carried by the yoke 115 against rotation about their axes. The belt 90, when wrapped around the driver roll 16 and the idler roll 114, will rotate the rolls 42, 41 as it is rotated by said driver roll and due to the canted axis of the idler roll, the belt 90 will move up the inclined plane toward the guide disc. As the roll 42v rotates, the bearing ring 144 will drive the guide disc 156 by means of the walls of the slots 145 engaging with the lugs 159 on the disc. As the disc 156 is rotated, the eccentric bearing surface of the retainer 150 will cause the disc to rotate about a different axis than the axis of the roll 114. As the disc rotates about an axis upwardly and rearwardly displaced with respect to the axis of rotation of the roll 114, th-e lugs 159 will slide radially in and out relative t0 the axis of the shaft 43 in the slots 145. The edge of the guide disc 156 will be flush with the surface of the roll 114 in the vicinity of the surface being dressed by the belt 90. The edge of the disc 156 gradually projects forward in overlapping relation with respect to the surface of the roll 114 as the distance from the working surface increases and reaches a maximum along the line drawn through the axis of the shaft 43 and the axisl of th-e center of the bearing surface 155 of the retainer 150.

In the embodiment of FIGURES 6 and 7, the guide disc 156 is positively rotated with the idler roll as the idler roll is rotated by the belt. In the embodiment of FIGURES 1-5, the guide disc 104 is freely rotatable about its axis such that the edge of the belt 90 engages with the guide portion of the disc to rotate the disc at the same speed as the belt.

With the guide discs 156 and 104 rotating at substantially the same speed as the belt, friction between the belt and disc is reduced to a minimum thereby reducing wear, heat and the expense of replacing worn parts.

The guide discs 156 and 104 are positioned relative tO the idler roll such as to not interfere with the belt in the vicinity of the working surface and still provide the guiding and centering function needed for the best operation of a belt type surface dressing mechanism.

We claim:

1. A surface dressing machine comprising a housing having a mounting base, a motor on said base, a driver roll supported for rotation about an axis below said base and being operatively connected to said motor, an idler roll supported for free rotation about an axis below said base and offset guide means rotatably mounted relative to said idler roll and relative to said base for retaining a surface dressing belt centered on said idler roll and on said driver roll.

2. A surface dressing machine comprising a housing having a mounting base, a motor on said base, a driver roll supported for rotation about an axis below said base and being operatively connected to said motor, an idler roll supported for free rotation about an axis below said base and offset guide means associated with said idler roll for retaining a surface dressing belt centered on said idler roll and on said driver roll, said means comprises a guide member pivoted about an axis offset from the axis of said idler roll and overlapping upwardly and rearwardly of the surface of the idler roll so as to be drivingly engaged by the side edge of said sanding belt for retaining said belt on the rolls.

3. A surface dressing machine as claimed in claim 1, wherein the axis of said idler roll in the direction of said guide means is canted slightly toward the axis of said driver roll so as to track said belt toward said guide member.

4. A surface dressing machine comprising a housing having a mounting base, a motor on said base, a driver roll supported for rotation about an axis below said base and being operatively connected to said motor, an idler roll supported for free rotation about an axis below said base, offset guide means rotatably mounted relative to said base for retaining a surface dressing belt centered on said idler roll and on said driver roll, said means is comprised of a disc shaped member having a diameter slightly larger than the diameter of said idler roll, a bearing member centrally disposed in said disc about which said disc freely rotates, said idler roll being mounted for rotation about its axis on a fixed shaft, and means for locking said bearing member to said fixed shaft of said idler roll along an axis offset upwardly from the axis of said fixed shaft whereby the edge of said dise overlaps the surface of said roll along the upper quadrant of said idler roll so that an edge of the surface dressing belt will engage with said overlapping portion of the disc for rotating said disc with said belt to retain said belt centered on said rolls.

5. A surface dressing machine comprising a housing having a mounting base, a motor on said base, a driver roll supported for rotation about an axis below said base and being operatively connected to said motor, an idler roll supported for free rotation about an axis below said base and offset guide means associated with said idler roll for retaining a surface dressing belt centered on said idler roll and on said driver roll, said means is freely rotatable relative to said idler roll about an axis offset with respect to the axis of the idler roll.

6. A surface dressing machine comprising a housing having a mounting base, a motor on said base, a driver roll supported for rotation about an axis below said base and being operatively connected to said motor, an idler roll supported for free rotation about an axis below said base, offset guide means rotatably mounted relative to said idler roll and relative to said base for retaining a surface dressing belt centered on said idler roll and on said driver roll, said means comprises a guide disc rotatably mounted about an axis offset relative to the fixed axis of said idler roll, means on said guide disc coacting with means on said idler roll whereby rotation of said idler roll will rotate said guide disc, and a portion of said disc overlapping the idler roll at least in one quadrant of said idler roll removed from the surface being dressed s as t0 retain said belt on said idler roll.

7. A surface dressing machine comprising a housing having a mounting base with a wall depending downwardly along one edge thereof, a driver roll lrotatably mounted on said Wall, power means carried by said base and operatively connected with said driver roll, an idler roll, means carried by said base for supporting said idler roll in spaced relation to said driver roll, said last named means comprising a yoke member supporting on one end a shaft for said idler roll and on the other end a pair of elongate members, said elongate members extending parallel to the base and operatively engaging with fixed coacting means carried by said base, spring means urging said yoke and idler roll away from said driving roll, and means carried by said base and removably engageable with said yoke member for holding said spring means depressed and said idler roll positioned in a position closer to said driving roll whereupon a surface dressing belt can be readily inserted over said rolls.

8. A surface dressing machine as claimed in claim 7 wherein means are provided on said idler roll for retaining said belt centered on said rolls, said last named means being freely rotatable relative to said idler roll.

9. A surface dressing machine as claimed in claim 8 wherein said pair of elongate members are comprised of rods fastened to said yoke member and slidably engaging said fixed coacting means carried on said base.

10. A surface dressing machine as claimed in claim 7 wherein said pair of elongate members are comprised of hollow tubular members carried by said fixed coacting means carried by said base and extending into coacting relation within openings in said yoke member, plug means in said openings and slidably engaging within the end portions of said tubular members, and said spring means nesting in said tubular members and bearing between said fixed means carried by said base and the end of said plug means for urging said yoke member away from said fixed means carried by said base.

11. A surface dressing machine as claimed in claim 7 wherein said pair of elongate members have a close sliding fit within openings in said yoke member whereupon rapid movement of said yoke member relative to the fixed coacting means on the base is prevented by the temporary vacuum created between said elongate members and the walls of said openings in said yoke.

12. A surface dressing machine as claimed in claim 7 wherein a dashpot is provided between said yoke and said fixed coacting means for preventing rapid movement of said idler roll relative to said driving roll.

References Cited UNITED STATES PATENTS 2,199,069 4/1940 Fowler 51-170 X 2,272,273 2/1942 Parker 51-170 2,893,176 7/1959 Bruck 51-170 3,094,819 6/1963 Murschel 51-170 3,176,436 4/1965 Anton 51-170 ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner U.S. Cl. X.R. 51-170 

